Elevated levels of sialic acid on the cell surface are highly correlated with the transformed phenotype in many cancers. This proposal aims to provide a chemical reporter approach toward the labeling and detection of specific glycans, sialic acid, present on the cell surface correlated with cancer and cancer progression. Using a well-developed protocol glycans will be labeled through the sialic acid salvage pathway providing a modified azidosugar allowing for the reaction with chemical reporter (cyclooctynes) to complete the 2-step bioorthogonal approach. In particular, this research will utilize bisarylcyclooctynes which are chose due to faster kinetics and enhanced chemical properties for biological systems. This proposal will significantly add to established research by testing a panel of chemical reporters as well as expanding into the area of MRI contrast agents providing greater clinical relevance toward this interesting class of compounds. These goals will be accomplished through the completion of four specific aims: (1) Synthesis of BARAC-fluorophores for optical imaging studies (2) Evaluate Ac4ManNAz metabolism and BARAC-fluorophore labeling in vivo (3) Synthesis of BARAC-Gd conjugate for contrast-enhanced MRI (4) In vivo evaluation of BARAC-Gd conjugates. Based on current research, it is hypothesized that utilizing the sialic acid salvage pathway will generate azidosugars allowing for reaction with cyclooctynes and thus the implementation of bioorthogonal smart probes which coupled with fluorescent probes and MRI contrast dyes will provide two different avenues for imaging and detection. A series of probes will be synthesized and evaluated using in vivo cancer/tumor models to determine the overall properties and probing capabilities in both the fluorescent probes and the MRI contrast dye probes.